Our studies in visual accommodation to date have led us to consider three important aspects: voluntary control, involuntary control, and interactions with eye movements. Surprisingly, we have shown that voluntary control of accommodation can be easily trained. This has interesting applications, and it emphasizes the caution needed in designing exppriments aimed at determining the nature of the accommodative control mechanism. Subjects readily learn to utilize even subtle cues that offer information on the polarity or magnitude of focus change. We also suspect that there is an involuntary control system involving only the central part of the fovea. A primary goal of this program is to establish the existence of this involuntary system and to determine its operational characteristics. These characteristics include the portion of the retina that is sensitive to accommodative stimuli, those aspects of the retinal blur pattern that drive accommodation, and the interaction between accommodation and miniature eye movements. These studies require an instrument that measures simultaneously the instantaneous direction of gaze of the eye and the instantaneous refractive power of the eye. During the first year of this grant, a composite instrument has been built that measures eye movements and refractive power simultaneously. This instrument may be regarded as a three-dimensional eye tracker.